chapter  1
4 Pages

Introduction

In recent years, fault-tolerant control has become a hot research area because of its importance in practical engineering [5, 54, 113, 121, 124, 134]. Generally, fault-tolerant control methods can be divided into passive faulttolerant method [84, 125, 133, 149, 164] and active fault-tolerant method [8, 9, 10, 11, 30, 46, 72, 94, 79, 130, 162]. A passive fault-tolerant controller commonly has a simple structure and is easily implemented [108, 117, 126]. The system performances in normal and fault modes can be optimized. However, as the number of faults increases, the design conservatism increases and even the design requirements cannot be achieved. On the other hand, an active fault-tolerant controller may readjust controller parameters or change controller structure to compensate the fault effects on systems [6, 19, 128, 131, 130, 129]. Many active fault-tolerant control methods are based on fault detection and diagnosis (FDD) mechanisms. Without FDD mechanisms, some methods have been developed to design fault-tolerant controllers using indirect adaptive method or direct adaptive method, based on the potentially adjustable capacity of adaptive method. The resultant closedloop system can be guaranteed to be stable, but the system performance in different modes cannot be optimized [8, 9, 10, 11, 130].